In the use of idler rollers it is known to have an idler roller system consisting of a fixed shaft having an idler roller rotatably mounted thereto, with an interposed bearing which facilitates the rotation of the idler roller about the shaft. It is also known to provide labyrinth seals for idler rollers. This combination of idler rollers and labyrinth seals is used, for example, with conveyor belts in mining and other operations. Labyrinth seals employ a tortuous network of passages between the contaminating environment and the idler roller bearing assembly. Contaminants can only infiltrate the bearing assembly by transversing the tortuous path. Idler roller failure is often caused by airborne moisture passing through the labyrinth seals.
During operation the temperature of an idler roller increases, for example, due to friction caused by a conveyor belt moving across the idler roller. This increase in temperature causes air inside the roller to expand and be expelled through the labyrinth seals. Thereafter, when the temperature of the roller decreases, the air inside the idler roller contracts. The air outside the idler roller is then drawn back inside the idler roller through the labyrinth seal. This air that is drawn into the idler roller contains moisture and contaminants which cause corrosion and damage to the bearings and races within the idler roller.
U.S. Pat. No. 9,133,940 describes a unidirectional labyrinth seal that allows air inside a roller to escape through the seal but blocks air from outside the roller from entering through the seal into the roller. Flexible annular fins positioned on a circular plate form an outer labyrinth seal. Annular ribs positioned on an end of an idler roller form an inner labyrinth seal. The fins project into recesses formed by the annular ribs, thereby forming the unidirectional annular labyrinth seal. The annular fins engage the annular ribs when the temperature of air within an interior of the roller is similar to the temperature of air exterior to the roller, thereby closing the labyrinth seal. The flexible annular fins bend away from the annular ribs when the temperature of air within the interior of the roller is higher than that of air exterior to the roller, thereby opening the labyrinth seal and allowing heated air within the interior of the roller to escape through the labyrinth seal. To replace the outer labyrinth seal it is necessary to provide a new plate with fins. It is difficult to obtain the best flexibility of the fins when they need to be formed as part of the plate. Since the inner labyrinth seal is part of the roller it is necessary to replace the whole roller to replace the inner labyrinth seal. What is needed is a unidirectional labyrinth seal system that is easier to construct and easily replaceable.